Pawel Pawlikowski talks about writing and directing the film “Ida,” set in Poland in 1962. It’s about Anna, an 18-year-old woman, preparing to become a nun at the convent where she has lived since she was orphaned as a child. Before taking her vows, she visits her mother’s sister and discovers is not only a former hard-line Communist state prosecutor who sentenced priests and others to death, but she's also a Jew. This revelation sets Anna on a journey to uncover her roots and confront the truth about her family. “Ida” opens May 2 at Film Forum and Lincoln Plaza Cinemas.